RE: Moultrie external battery thingy
I see no problem on hooking up and external battery as long as it's 6 volt.
I would drill a hole amd run the wires up through the bottom to keep rain/water from entering.
I am running Cabela's 4.1's with rechargable 4.5ah batteries and solar chargers. I just checked 2 of them and in 10 days one took 1100 pics and the other 1800. The camera that took the 1100 pictures had a charge of 99% according to the camera and the camera that took 1800 pics had a battery charge of 66%, this was due to the solar chargerwires coming off . They do take alot of flash pictures also. They have been working great for me. A note though, these are in the warm climates of South Texas